Magnet Unit, Elevator Guiding Apparatus and Weighing Apparatus

ABSTRACT

A magnet unit includes a first magnetic pole ( 7   a ), a second magnetic pole ( 7   b ) and a third magnetic pole ( 7   c ) at a center between the first magnetic pole ( 7   a ) and the second magnetic pole ( 7   b ), providing an E-shaped configuration. In the magnet unit, a first magnet is defined between the first magnetic pole ( 7   a ) and the third magnetic pole ( 7   c ) by connecting two electromagnets ( 71   aa   , 73   aa ) with each other through a permanent magnet ( 72   a ), while a second magnet is defined between the second magnetic pole ( 7   b ) and the third magnetic pole ( 7   c ) by connecting two electromagnets ( 71   ba   , 73   ba ) with each other through a permanent magnet ( 72   b ). With this configuration, it is possible to reduce a deviation in the length of respective magnetic paths from the permanent magnets ( 72   a   , 72   b ) up to their respective magnetic poles. By controlling exciting currents to the respective magnetic poles. By controlling exciting currents to the respective electromagnets ( 71   aa,    73   aa,    71   ba   , 73   ba ), it is also possible to adjust fluxes (or flux density) in respective directions x, y individually.

TECHNICAL FIELD

The present invention relates to the improvement of a magnet unit thatis preferred to an elevator guiding apparatus and the like.

BACKGROUND ART

In an elevator, generally, guide rails are arranged in pairs on anelevator shaft vertically. Being guided by these guide rails, anelevator car suspended by a main rope moves up and down the elevatorshaft.

In order to allow the elevator car to be guided along the guide rails, aguide device is mounted on a car frame of the elevator car.

There are a roller-type guide device and a guide shoe-type guide device.Since these guide devices guide the elevator car with being in contactwith the guide rails directly, these guide devices are predisposed togenerate vibrations and noises due to distortion and connections of theguide rails, so such vibrations and noises are easily propagated intothe elevator car though rollers and the like.

Thus, an elevator guiding apparatus that adopts a magnet unit for theguide rails is proposed (e.g. Japanese Patent Application Laid-open No.2001-19286). In the elevator guiding apparatus, an attracting force of amagnet is generated between the opposing guide rails made of iron,guiding the elevator car in a non-contact manner, based on detectionsignals of a gap sensor.

FIG. 1 is a perspective view of the substantial part of theabove-mentioned conventional elevator guiding apparatus. FIG. 2 is aplan view of a magnetic circuit of the magnet unit of FIG. 1.

As shown in FIGS. 1 and 2, the magnet unit 1 having an E-shapedconfiguration includes a center core 11, permanent magnets 12 a, 12 bconnected to both sides of the center core 11 to have respectiveidentical poles opposing to each other and electromagnets 13 a, 13 bconnected to the permanent magnets 12 a, 12 b respectively to haverespective identical poles opposing each other.

In FIG. 1, the magnet unit 1 is provided with a plurality of sensors 2having gap sensors. The sensors 2 are adapted so as to detect thecondition of a magnetic circuit (magnetic path) at gaps between thepoles of the magnet unit 1 and a guide rail 3 in both of x, y directions(horizontal direction), in other words, detecting a physical quantity inthe magnetic circuit.

As the elevator guiding apparatus controls attraction forces between theelectromagnets 13 a, 13 b and the guide rail 3 in accordance with theexciting current control of the electromagnets 13 a, 13 b based ondetection signals of the sensors 2, a not-shown elevator car equippedwith the elevator guiding apparatus can move up and down in the elevatorshaft while maintaining a non-contact condition between the apparatusand the guide rail 3.

In the elevator guiding apparatus using the above-constructed magnetunit, when the elevator car is in a normal position to the guide rail 3and its operation is stable, it is possible to make exciting currentsfor coils 13 aa, 13 ba converge to zero, that is, so-called “zero powercontrol” owing to the possession of the permanent magnets 12 a, 12 b.Accordingly, it is possible to suppress electric power consumption inthe stationary state. Additionally, owing to the provision of thepermanent magnets, an interval between the guide rail 3 and the magnetunit 1 could be broadened furthermore to allow the elevator car toelevate smoothly along the guide rail 3 with a long stroke and a lowrigidity.

Note that, in the elevator guiding apparatus for guiding the movement ofthe elevator car along the guide rails 3, there are sensors 2 and magnetunits 1 arranged at four (up, down, left and right) positions about theelevator car, facing the guide rails 3. In operation, with a calculationbased on signals from the sensors 2 to detect the conditions of magneticcircuits at respective gaps between the guide rail 3 and the magnet unit1 and signals from the magnet units 1 to detect exciting currents, afeedback control is applied on the exciting currents.

Regarding FIGS. 1 and 2, it is defined here that “x” represents adirection along which the magnet unit 1 opposes the guide rail 3(generally, left-and-right direction of the elevator car viewed from itsentrance side); “y” represents a direction perpendicular to thedirection x in a horizontal plane (i.e. a depth direction of theelevator car); and “z” represents a vertical direction. In connection,“ξ”, “θ” and “φ” represents rotating directions around the directions x,y and z as axes of rotation.

Since the above-mentioned elevator guiding apparatus is constructed soas to control the magnet units 1 at four positions with a calculationbased on respective signals from the upper and lower sensors 2 in thedirections x and the upper and lower sensors 2 in the direction y todetect length of gaps and also based on respective values of excitingcurrents on detection, the elevator car is capable of moving up and downwhile being guided by the guide rails 3 under posture controls about“rolling direction” (i.e. the direction θ), “pitching direction” (i.e.the direction ξ) and “yawing direction” (i.e. the direction φ) as wellas the translating movement in the directions x and y.

The magnet unit 1 shown in FIG. 2, however, has a problem described asfollows.

For the description, firstly, left and right long surfaces in thesection of the guide rail 3 are defined as a first guide face 3 a and asecond guide face 3 b respectively, while a short surface of the sectionis defined as a third guide face 3 c. Correspondingly, respectivemagnetic poles of the magnet unit 1 respectively opposing the guidefaces 3 a, 3 b and 3 c are defined as a first magnetic pole 1 a, asecond magnetic pole 1 b and a third magnetic pole 1 c, respectively. InFIG. 2, two-dotted lines with arrows denote magnetic flux lines bypermanent magnets 12 a, 12 b. Consequently, it will be understood thatmagnetic flux (or flux density) at the third magnetic pole 1 c becomeslarger than magnetic flux (or flux density) at the first magnetic pole 1a or the second magnetic pole 1 b since magnetic flux lines of thepermanent magnets 12 a, 12 b are superimposed on each other at the thirdmagnetic pole 1 c.

Additionally, it is noted that the shorter a magnetic path from apermanent magnet up to a magnetic pole gets, the smaller a leakage offlux from the permanent magnet becomes. Therefore, the flux density atthe third magnetic pole 1 c becomes larger than the flux density at thefirst magnetic pole 1 a or the same at the second magnetic pole 1 bbecause of a difference in respective magnetic paths between thepermanent magnets 12 a, 12 b and the magnetic poles 1 a, 1 b, 1 c.

Consequently, an attraction force generated between the third guide face3 c and the third magnetic pole 1 c is remarkably large in comparisonwith an attraction force between the first guide face 3 a and the firstmagnetic pole 1 a or between the second guide face 3 b and the secondmagnetic pole 1 b.

The conventional magnet unit 1 mentioned above is generally used for anelevator guiding apparatus or a weighing apparatus for measuring aweight of an object in a non-contact manner. In the case of adopting themagnet unit 1 in the elevator guiding apparatus, however, the stabilityof an elevator car in its equilibrium situation is damaged due to theabove difference of attraction force in between the backward-and-forwarddirection (i.e. the direction y) and the left-and-right direction (i.e.the direction x). Additionally, the magnets unit's reaction forcesreactive to disturbance applied to the elevator car are different fromeach other depending on displacement directions of the elevator car.

The electromagnets 13 a, 13 b of the conventional magnet unit 1 have agreat influence on the first magnetic pole 1 a and the second magneticpole 1 b, respectively. While, the electromagnets 13 a, 13 b have littleinfluence on the third magnetic pole 1 c because of interposition of thepermanent magnets 12 a, 12 b.

In this way, the conventional magnet unit 1 has great differences inboth attraction force and controllability between the directions (i.e.the direction x and the direction y) since the controllability of theelectromagnets 13 a, 13 b against the third magnetic pole 1 c is smallwhile an attraction force of the permanent magnets 12 a, 12 b at thepole 1 c is large. Accordingly, an elevator guiding apparatus adoptingthe above magnet unit (s) or the like has a reduced stability inoperation since both responsibility and controllability of the magnetsare different from each other depending on the directions.

In order to contemplate equalization in controllability withcompensation for the reduced controllability of the electromagnets 13 a,13 b to the third magnetic pole 1 c, it might be supposed to supply theelectromagnets 13 a, 13 b with great exciting currents in a moment oftime. However, this measure is accompanied with great electric powerconsumption, requiring a capacious power source.

DISCLOSURE OF INVENTION

In the above-mentioned situation, it is an objective of the presentinvention to provide a magnet unit that can accomplish a reduction ofdeviations of attraction forces of permanent magnets due to thedirections of the magnetic forces and can enhance their controllabilityto respective magnetic poles, thereby allowing a reduction in thecapacity of a power source. Another objective of the invention is toprovide an elevator guiding apparatus and the like having such a magnetunit and operates stably with high efficiency.

In order to achieve the above objectives, according to the first aspectof the present invention, there is provided a magnet unit having anE-shaped configuration, comprising: first and second magnetic polesopposed to each other, having same polarity; a third magnetic polearranged at a center between the first magnetic pole and the secondmagnetic pole, having different polarity from that of the first andsecond magnetic poles; a first magnet defined between the first magneticpole and the third magnetic pole, the first magnet having twoelectromagnets connected with each other through the intermediary of apermanent magnet; and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet.

With the above configuration of both the first magnet and the secondmagnet, a deviation in magnetic paths from each permanent magnet up torespective magnetic poles of the magnet unit is reduced, and fluxes (orflux densities) at respective magnetic poles can be controlledindividually.

That is, since the directional deviation in the attraction forces of thepermanent magnets is reduced with an improvement in the controllabilityof the exciting currents to respective magnetic poles, it is possible toprovide a magnet unit which is well-balanced in operation and furtherstable in both responsibility and controllability in operation.

Additionally, according to the present invention, there is also providedan elevator guiding apparatus comprising: a magnet unit having anE-shaped configuration, including first and second magnetic polesopposed to each other, having same polarity, a third magnetic polearranged at a center between the first magnetic pole and the secondmagnetic pole, having different polarity from that of the first andsecond magnetic poles, a first magnet defined between the first magneticpole and the third magnetic pole, the first magnet having twoelectromagnets connected with each other through the intermediary of apermanent magnet, and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet, wherein that the first, second and thirdmagnetic poles are arranged so as to oppose a guide member made ofmagnetic material through respective gaps; a plurality of sensors fordetecting respective conditions of magnetic circuits in the magnet unit;and a control unit for controlling exciting currents supplied to theelectromagnets of the magnet unit based on output signals from thesensors.

In the above elevator guiding apparatus, as the control unit controlsthe exciting currents of the magnet unit based on output signals fromthe sensors, there are obtained, between the guide rail and the magnetunit, appropriate attraction forces and controllability both havingsmall deviations in directions, allowing the elevator car to travel inan elevator shaft stably.

Further, according to the present invention, there is also provided aweighing apparatus comprising: a movable body for mounting an object tobe measured, the movable body having a plurality of magnet unitsattached to sidewalls of the movable body on exterior sides, the magnetunit having an E-shaped configuration, the magnet unit including firstand second magnetic poles opposed to each other, having same polarity, athird magnetic pole arranged at a center between the first magnetic poleand the second magnetic pole, having different polarity from that of thefirst and second magnetic poles, a first magnet defined between thefirst magnetic pole and the third magnetic pole, the first magnet havingtwo electromagnets connected with each other through the intermediary ofa permanent magnet, and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet; a frame for supporting the movable bodymovable in a vertical direction and provided with a plurality of guidemembers made of magnetic material corresponding to the magnet units,respectively; a plurality of sensors for detecting respective conditionsof magnetic circuits in the magnet units at respective gaps each betweenthe magnetic poles of the magnet units and the guide member; and acontrol unit for controlling exciting currents to electromagnets of themagnet units based on output signals from the sensors.

Still further, according to the present invention, there is alsoprovided another weighing apparatus comprising: a movable body formounting an object to be measured, the movable body having a pluralityof guide member made of magnetic material attached to sidewalls of themovable body on exterior sides; a frame for supporting the movable bodymovable in a vertical direction and provided with a plurality of magnetunits facing the guide members, the magnet unit having an E-shapedconfiguration, the magnet unit including first and second magnetic polesopposed to each other, having same polarity, a third magnetic polearranged at a center between the first magnetic pole and the secondmagnetic pole, having different polarity from that of the first andsecond magnetic poles, a first magnet defined between the first magneticpole and the third magnetic pole, the first magnet having twoelectromagnets connected with each other through the intermediary of apermanent magnet, and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet; a plurality of sensors for detectingrespective conditions of magnetic circuits in the magnet units atrespective gaps each between the magnetic poles of the magnet unit andthe guide member; and a control unit for controlling exciting currentsto electromagnets of the magnet units based on output signals from thesensors.

In each of above weighing apparatuses, as the control unit controls theexciting currents of the magnet unit based on output signals from thesensors, there can be attained, between the guide member and the magnetunit, appropriate attraction forces and controllability both havingsmall deviations in directions, allowing the weight of the object to bemeasured stably and effectively.

These and other objectives and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompanied drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a conventional magnet unit;

FIG. 2 is a plan view showing a magnetic circuit of the magnet unit ofFIG. 1;

FIG. 3 is a structural view of an elevator having an elevator car in itselevating movement and equipped with an elevator guiding apparatushaving a magnet unit in accordance with the first embodiment of thepresent invention;

FIG. 4 is an enlarged perspective view of a substantial part of theelevator guiding apparatus of FIG. 3;

FIG. 5 is a perspective view of the magnet unit of FIG. 4, viewed fromthe opposite side;

FIG. 6 is a plan view showing a magnetic circuit of the magnet unit ofFIG. 4;

FIG. 7 is a structural view of a circuit of the elevator guidingapparatus of FIG. 3;

FIG. 8 is a plan view of a magnetic circuit of the magnet unit inaccordance with the second embodiment of the present invention;

FIG. 9 is a structural view of a weighing apparatus having the magnetunit of the present invention; and

FIG. 10 is a sectional view taken along a line 10-10 of a frame of FIG.9.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to FIGS. 3 to 10, an embodiment of a magnet unit of thepresent invention, an embodiment of an elevator apparatus having themagnet unit of the invention and an embodiment of a weighing apparatusalso having the magnet unit will be described below. Note that, in theseembodiments, like elements to those of the prior art magnet unit and theprior art elevator guiding apparatus of FIGS. 1 and 2 are indicated withlike reference numerals, respectively. Their overlapping descriptionsare eliminated.

FIG. 3 is a side view of an elevator equipped with the elevator guidingapparatus. The elevator guiding apparatus shown in this figure adoptsthe magnet unit in accordance with one embodiment of the presentinvention.

As shown in FIG. 3, a pair of guide rails 3, 3 made from ironferromagnetic bodies are laid vertically in an elevator shaft 4. Anelevator car 6 suspended by ropes 5 moves up and down while being guidedby the guide rails 3, 3.

At four corners of a car frame of the elevator car 6, E-shaped magnetunits 7 respectively opposing the guide rails 3, 3 and serve as a guidedevice, and sensors 2 for detecting respective conditions of magneticcircuits (magnetic paths) in gaps between respective poles of the magnetunits 7 and the guide rails 3, 3, are attached to the elevator car 6through pedestals 8. The pedestals 8 made of non-magnetic material, suchas aluminum, stainless steel and plastics, are fixed to the car frame ofthe elevator car 6.

Note that left and right direction in the figure, that is, thehorizontal direction to the elevator car 6 is defined as “x direction”;the direction of the normal line to the figure is defined as “ydirection”; and the vertical direction is defined as “z direction” inFIG. 1. Similarly, respective rotating directions around the respectivex, y, z directions as axes of rotation are defined as “ξ, θ, φdirections”, respectively.

Each of the sensors 2 is formed by a so-called “gap sensor” fordetecting an interval (distance) between each pole of the E-shapedmagnet unit 7 and the guide rail 3.

FIG. 4 is an enlarged perspective view of the substantial part of FIG. 3and FIG. 5 is a perspective view of the magnet unit 7 of FIG. 4, viewedfrom the opposite side.

FIG. 6 is a plan view of a magnetic circuit of the magnet unit 7 of FIG.5, including the guide rail 3 opposing the unit 7.

With regard to respective surfaces of the guide rail 3 opposing theE-shaped magnet unit 7, two opposing surfaces of the guide rail 3perpendicular to the direction y are defined as a first guide face 3 aand a second guide face 3 b, respectively, as shown in FIGS. 4 and 6.One surface of the guide rail 3 perpendicular to the direction x isdefined as a third guide face 3 c.

While, as shown in FIGS. 5 and 6, the E-shaped magnet unit 7 includes afirst electromagnet 71 a and a second electromagnet 71 b arranged so asto oppose the first guide face 3 a and the second guide face 3 b of theguide rail 3, respectively, and a center electromagnet 73 composed ofthird and fourth electromagnets 73 a, 73 b arranged so as to oppose thethird guide face 3 c. Respective coils 71 aa, 71 ba, 73 aa, 73 ba arewound about the electromagnets 71 a, 71 b, 73 a, 73 b and furthersupplied with exciting currents, respectively.

The first and second electromagnets 71 a, 71 b are connected to thethird and fourth electromagnets 73 a, 73 b through a first permanentmagnet 72 a and a second permanent magnet 72 b, respectively. The firstand second permanent magnets 72 a, 72 b are arranged so that theirrespective identical poles oppose each other.

A first magnetic pole 7 a, a second magnetic pole 7 b and a thirdmagnetic pole 7 c are formed at both ends of the first and secondelectromagnets 71 a, 71 b and one end of the center electromagnet 71 copposing the first, second and third guide faces 3 a, 3 b and 3 c,respectively. The first permanent magnet 72 a connects the firstelectromagnet 71 a with the third electromagnet 73 a to form one magnet.The second permanent magnet 72 b connects the second electromagnet 71 bwith the fourth electromagnet 73 b to form another magnet.

That is, since the permanent magnets 72 a, 72 b have respective bothends connected to the electromagnets 71 a, 73 a and 71 b, 73 b, adeviation in magnetic paths from the magnets 72 a, 72 b up to therespective magnetic poles (7 a, 7 c; 7 b, 7 c) becomes smaller, so thatthere is no great difference in leakage flux in the course of reachingthe respective poles.

In the above-constructed magnet unit 7, the directions of magnetic linesof the first and second poles 7 a, 7 b opposing each other through theguide rail 3 are substantially perpendicular to the direction ofmagnetic lines of the third pole 7 c. Further, the first pole 7 a, thesecond pole 7 b and the third pole 7 c are arranged to oppose the firstguide face 3 a, the second guide face 3 b and the third guide face 3 c,respectively, through the intermediary of gaps (intervals). Accordingly,by controlling exciting currents to the electromagnets 71 a, 71 b, 73 a,73 b, it is possible to adjust an attraction force of the magnet unit 7to the guide rails 3. In detail,

(1) if supplying the exciting currents to the electromagnets 71 a, 71 b,73 a, 73 b in a direction to strengthen magnetic fluxes of the permanentmagnets 72 a, 72 b,

(1-1) since attraction forces between the first and second poles 7 a, 7b and the first and second guide faces 3 a, 3 b of the guide rail 3 areincreased at the same level as each other, respective increments in theattraction forces in the direction y cancel each other as a resultantforce, the attraction force hardly changes; and

(1-2) since the magnetic flux between the third pole 7 c of the thirdguide faces 3 c of the guide rail 3 is increased, the resultingattraction force is increased in the direction x.

(2) If supplying the exciting currents to the electromagnets 71 a, 71 b,73 a, 73 b in a direction to weaken magnetic fluxes of the permanentmagnets 72 a, 72 b,

(2-1) since attraction forces between the first and second poles 7 a, 7b and the first and second guide faces 3 a, 3 b of the guide rail 3 aredecreased at the same level as each other, respective decrements in theattraction forces in the direction y cancel each other as a resultantforce, the attraction force hardly changes; and

(2-2) since the magnetic flux between the third pole 7 c of the thirdguide faces 3 c of the guide rail 3 is decreased, the resultingattraction force is decreased in the direction x.

(3) If supplying the exciting currents to the first and thirdelectromagnets 71 a, 73 a in a direction to strengthen magnetic flux ofthe permanent magnet 72 a and also supplying the exciting currents tothe second and fourth electromagnets 71 b, 73 b in a direction to weakenmagnetic flux of the permanent magnet 72 b,

(3-1) since the magnetic flux increases on the side of the first pole 7a while the magnetic flux decreases on the side of the second pole 7 bin the direction y, a difference in attraction force is produced in theleft-and-right direction of the guide rail 3, so that the magnet unit 7is absorbed toward the first guide face 3 a for approach; and

(3-2) the change of magnetic flux about the third pole 7 c is cancelledso that the attraction force hardly changes.

Note that, in connection with the above item (3), if supplying theexciting currents to the first and third electromagnets 71 a, 73 a in adirection to weaken magnetic flux of the permanent magnet 72 a and alsosupplying the exciting currents to the second and fourth electromagnets71 b, 73 b in a direction to strengthen magnetic flux of the permanentmagnet 72 b, there is no change in the direction x for stabilization,while the magnet unit 7 is absorbed toward the second guide face 3 b forapproach in the direction y.

As mentioned above, according to the above-constructed magnet unit 7, bycontrolling the exciting currents the first and second electromagnets 71a, 71 b and the third and fourth electromagnets 73 a, 73 b forming thecenter electromagnet 73, it is possible to adjust the attraction forcesof the magnet unit 7 on the guide rail 3 in the directions x and yindividually.

In the above description, the control of exciting currents to increaseand decrease the fluxes of the first and second permanent magnets 72 a,72 b can be accomplished by connecting the coils 71 aa, 73 aa of theelectromagnets 71 a, 73 a and the coils 71 ba, 73 ba of theelectromagnets 71 b, 73 b in series.

As obvious from above, on condition of adopting the above-mentionedmagnet unit 7 of the first embodiment as the elevator guiding apparatusand further installing four units 7 to four (up, down, left and right)corners of the elevator car 6 through the pedestals 8 together with thesensors 2 while opposing the guide rails 3, the control of excitingcurrents to the respective electromagnets allows, the elevator car 6 tobe posture-controlled to a translational direction (i.e. x-y directions)in the horizontal plane and a rotational direction (i.e., ξ, θ, φdirections), whereby non-contact and stable guide control of theelevator car 6 to the guide rails 3 can be accomplished.

FIG. 7 is a structural view of a circuit of the elevator guidingapparatus provided by adding a controller to the magnet unit 7 of thefirst embodiment and the sensors 2. Thus, the elevator guiding apparatusincludes the electromagnets 71 a, 71 b, 73 a, 73 b of the magnet unit 7,the sensors 2 for detecting physical values in the magnetic circuit(path) formed by the magnet unit 7 through the guide rail 3, forexample, gap sensors for detecting the sizes of gaps between therespective poles of the unit 7 and the guide rail 3 in both directions xand y, and a current detector 91, a calculating circuit 92 and a poweramplifier 93.

Inputting detection signals from the current detector 91 for detectingvalues of exciting currents flowing the electromagnets and signals fromthe sensors 2, as heretofore, the calculating circuit 92 calculatesvoltage values to be applied on the electromagnets 71 a, 71 b, 73 a, 73b of the magnet unit 7 and further supplies the voltages to them throughthe power amplifier 93. Therefore, according to the elevator guidingapparatus, it is possible to accomplish a stable guide control of theelevator car 6 with uniform attraction force having no directionaldeviation in the horizontal direction to the guide rails 3, 3 and alsouniform controllability.

In a normal state of the position of the elevator car 6 with respect tothe guide rails 3, 3, it is possible to allow the exciting currents ofthe magnet unit 7 to converge to zero irrespective of changes in weightof the elevator car 6 and its magnitude of a disproportional force,whereby the elevator car 6 can be guided by only magnetic forces of thepermanent magnets 72 a, 72 b, that is, “zero-power control”, and thusthe elevator car 6 is stabilized.

Note, in the above description, respective end faces of the poles of themagnet unit 7 may be covered with solid lubricating members made ofmaterial including e.g. Teflon (registered trademark), carbon ormolybdenum disulfide, allowing the elevator car 6 to elevate smoothlydue to sliding using such solid lubricating members.

Repeatedly, according to the embodiment, the permanent magnets 72 a, 72b are arranged on both sides of the magnet unit 7, and theelectromagnets 71 a, 73 a; 71 b, 73 b are arranged on both sides of thepermanent magnets 72 a, 72 b, respectively. With the arrangement likethis, since there is less difference between a distance (magnetic path)from the permanent magnet 72 a to its magnetic pole and another distance(magnetic path) from the other permanent magnet 72 b to its magneticpole, a deviation of fluxes at the respective magnetic poles is reduced.Consequently, the difference of attraction force in between thedirection x and the direction y is decreased to provide the magnet unit7 under an appropriately-balanced condition.

Additionally, according to the embodiment, since the magnet unit 7 hasthe center electromagnet 73 arranged between the electromagnets 72 a and72 b and the center electromagnet 73 makes it possible to easily controlan attraction force in the direction x, the individual controllabilityof the attraction force to the directions x and y is improved as awhole.

Note that, in the above-mentioned magnet unit 7 for the elevator guidingapparatus, the center electromagnet 73 is formed by two electromagnets73 a, 73 b. In a modification, if only arranging electromagnets on bothsides of the permanent magnets 72 a, 72 b each, the number ofelectromagnets may be decreased to construct the center electromagnet 73by one common coil winding.

The second embodiment where the center electromagnet 73 of the magnetunit 7 is formed by the single electromagnet will be described withreference to FIG. 8.

As shown in this figure corresponding to FIG. 8 of the first embodiment,an electromagnet 73 c is arranged at a projecting part of the third pole7 c of the center electromagnet 73 to form a magnetic circuit (magneticpath) in common with the permanent magnets 72 a, 72 b.

Similar to the first embodiment, a magnetic path between the permanentmagnet 72 a and its pole is substantially equal to that between thepermanent magnet 72 b and its pole. Thus, while a difference in theattraction force between the directions becomes small, by controllingthe exciting currents to the respective electromagnets 71 a, 72 b, 73 cbased on the sensors 2 in the adoption of the elevator guidingapparatus, it is possible to control attraction forces in bothdirections x and y individually, allowing the elevator car 6 to becontrolled between the guide rails 3 in a non-contact manner in thehorizontal direction.

By reason that the magnet unit 7 in common with the first and secondembodiments allows the attraction forces in both directions x and y tobe controlled individually thereby attaining the guide of the elevatorcar 6 as a moving body in a non-contact manner in the horizontaldirection due to zero-power control, the magnet unit 7 may be applied toa known weighing apparatus for measuring the weight of an object.

One embodiment of the weighing apparatus adopting the magnet unit 7 ofthe present invention will be described with reference to FIGS. 9 and10.

FIG. 9 is a structural view showing the embodiment of the weighingapparatus of the invention. FIG. 10 is a sectional view taken along aline 10-10 of a frame in FIG. 9.

In the weighing apparatus 10, as already known, the upper part of theframe 101 is provided, on its interior side, with a magnet unit 102 forlevitation control directing downwardly. A movable body 103 is includedin the frame 101. While, the upper portion of the movable body 103 isprovided, on its exterior side, with a guide 103 for magnetic levitationmade of ferromagnetic material, such as iron, in an opposite position tothe magnet unit 102.

The movable body 103 is attracted by the magnet unit 102 attached to theceiling of the frame 101. On the upper part of the frame 101 and on theinterior side, there are gap sensors 102 a, 102 a for detecting thesizes of gaps each between the magnet unit 102 and the guide 103 a. Onrespective inner sidewalls of the frame 101 and at upper and lowerpositions, a pair of E-shaped magnet units 7, 7 in each sidewall arearranged so as to each interleave the guide members 3 in the form ofrails from both sides thereof. Each of the guide members 3 is made offerromagnetic material and attached to the movable body 103. As similarto the elevator guiding apparatuses of the first and second embodiments,the frame 101 is further provided with sensors 2 for detecting theconditions of magnetic circuits (i.e. physical value) at respective gapseach between the pole of the magnet unit 7 and the guide member 3.

Signals from the gap sensors 102 a for magnetic levitation and therespective sensors 2 are transmitted to a control processor 105. Then,the control processor 105 controls the operations of respectiveelectromagnets in both the magnet unit 102 and the magnet units 107 inthe similar way.

Here, if an object 104 to be measured is mounted inside the movable body103, then it is subjected to a load. In this state, the controlprocessor 105 calculates the weight of the object 104, based on anattraction force and gap both generated between the magnet unit 102lifting up the movable body 103 stably and the guide 103 a.

In FIG. 9, left and right direction in figure is defined as “xdirection”; a direction of a normal line to the figure is defined as “ydirection”; and the vertical direction is defined as “z direction”.Respective rotating directions around the respective x, y, z directionsas axes of rotation are defined as “ξ, θ, φ directions”, respectively.In the weighing apparatus, the control of translating movement of themovable body 103 in the direction z is assumed by the magnet unit 102,while the other translating movements in the directions x, y and thecontrol of the rotational movements in the directions ξ, θ, φ areassumed by the magnet units 7.

That is, with the similar principle to those of the elevator guidingapparatuses of the first and second embodiments regarding both cross andhorizontal directions (both directions x, y), it is possible to supportthe movable body 3 corresponding to the elevator car 6 horizontally in anon-contact manner.

According to the embodiment, the guide members 3 are mounted on themovable body 103, while both. of the magnet units 7 and the sensors 2are mounted on the frame 101. Therefore, since there is no need toarrange any component for power supply on the side of the movable body103, it is possible to simplify the structure of the movable body 103.

Note that there is need to arrange components for power supply on theside of the frame 101 due to the arrangement of the magnet units 7 andthe sensors 2 on the side of the frame 101 in the above-mentionedweighing apparatus of FIGS. 9 and 10. In a modification, the magnetunits 7 and the sensors 2 may be arranged on the side of the movablebody 103 on condition of arranging the guide members 3 on the side ofthe frame 101.

In any case, according to the weighing apparatus adopting the magnetunit 7 of the invention, it is possible to realize an improvedcontrollability in the directions of respective axes and it is alsopossible to provide a well-balanced and stable weighing apparatus.

1. A magnet unit having an E-shaped configuration, comprising: first andsecond magnetic poles opposed to each other, having same polarity; athird magnetic pole arranged at a center between the first magnetic poleand the second magnetic pole, having a different polarity from that ofthe first and second magnetic poles; a first magnet defined between thefirst magnetic pole and the third magnetic pole, the first magnet havingtwo electromagnets connected with each other through the intermediary ofa permanent magnet; and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet.
 2. The magnet unit of claim 1, wherein thefirst, second and third magnetic poles are arranged so as to oppose aguide member of magnetic material through respective gaps, the magnetunit further comprises sensors adapted to detect respective conditionsof magnetic circuits in the magnet unit.
 3. An elevator guidingapparatus comprising: a magnet unit having an E-shaped configuration,including first and second magnetic poles opposed to each other, havingsame polarity, a third magnetic pole arranged at a center between thefirst magnetic pole and the second magnetic pole, having a differentpolarity from that of the first and second magnetic poles, a firstmagnet defined between the first magnetic pole and the third magneticpole, the first magnet having two electromagnets connected with eachother through the intermediary of a permanent magnet, and a secondmagnet defined between the second magnetic pole and the third magneticpole, the second magnet having two electromagnets connected with eachother through the intermediary of another permanent magnet, wherein thatthe first, second and third magnetic poles are arranged so as to opposea guide member made of magnetic material through respective gaps; aplurality of sensors for detecting respective conditions of magneticcircuits in the magnet unit; and a control unit for controlling excitingcurrents supplied to the electromagnets of the magnet unit based onoutput signals from the sensors.
 4. The elevator guiding apparatus ofclaim 3, wherein the control unit controls the exciting currents so thatthe magnetic circuits are stabilized while the exciting currents to theelectromagnet are zero.
 5. A weighing apparatus comprising: a movablebody for mounting an object to be measured, the movable body having aplurality of magnet units attached to sidewalls of the movable body onexterior sides, the magnet unit having an E-shaped configuration, themagnet unit including first and second magnetic poles opposed to eachother, having same polarity, a third magnetic pole arranged at a centerbetween the first magnetic pole and the second magnetic pole, having adifferent polarity from that of the first and second magnetic poles, afirst magnet defined between the first magnetic pole and the thirdmagnetic pole, the first magnet having two electromagnets connected witheach other through the intermediary of a permanent magnet, and a secondmagnet defined between the second magnetic pole and the third magneticpole, the second magnet having two electromagnets connected with eachother through the intermediary of another permanent magnet; a frame forsupporting the movable body movable in a vertical direction and providedwith a plurality of guide members made of magnetic materialcorresponding to the magnet units, respectively; a plurality of sensorsfor detecting respective conditions of magnetic circuits in the magnetunits at respective gaps each between the magnetic poles of the magnetunits and the guide member; and a control unit for controlling excitingcurrents to electromagnets of the magnet units based on output signalsfrom the sensors.
 6. The weighing apparatus of claim 5, wherein thecontrol unit controls the exciting currents so that the magneticcircuits are stabilized while the exciting currents to the electromagnetare zero.
 7. A weighing apparatus comprising: a movable body formounting an object to be measured, the movable body having a pluralityof guide member made of magnetic material attached to sidewalls of themovable body on exterior sides; a frame for supporting the movable bodymovable in a vertical direction and provided with a plurality of magnetunits corresponding to the guide members, the magnet unit having anE-shaped configuration, the magnet unit including first and secondmagnetic poles opposed to each other, having same polarity, a thirdmagnetic pole arranged at a center between the first magnetic pole andthe second magnetic pole, having different polarity from that of thefirst and second magnetic poles, a first magnet defined between thefirst magnetic pole and the third magnetic pole, the first magnet havingtwo electromagnets connected with each other through the intermediary ofa permanent magnet, and a second magnet defined between the secondmagnetic pole and the third magnetic pole, the second magnet having twoelectromagnets connected with each other through the intermediary ofanother permanent magnet; a plurality of sensors for detectingrespective conditions of magnetic circuits in the magnet units atrespective gaps each between the magnetic poles of the magnet unit andthe guide member; and a control unit for controlling exciting currentsto electromagnets of the magnet units based on output signals from thesensors.
 8. The weighing apparatus of claim 7, wherein the control unitcontrols the exciting currents so that the magnetic circuits arestabilized while the exciting currents to the electromagnet are zero.